Inner and middle ear tissues are among the most difficult to properly fix, orient and section for routine light and electron microscopy. However, this approach is crucial to obtain a proper understanding of the development and aging, function, disease processes and recovery of the inner and middle ear. The goal of the Histology Core is to provide the necessary training and/or services that will enable any investigator to routinely examine inner ear and related structures. Tissues of interest include, but are not limited to the sensory epithelium, bone and nervous system. The core provides full service histology, training and equipment use for frozen tissues or tissues embedded in paraffin as well as methacrylate and epoxy resins. Thin sectioning for electron microscopy is also available as are a wide variety of counterstaining and enzyme staining procedures. The specific aims of the Histology Core are: 1) to ensure that member investigators utilize optimal histological processing of desired tissues through consultation, training, supervision and evaluation of results as well as through the provision of technical services; 2) to promote collaborative efforts between core members as well as outside investigators; and 3) to promote the rapid systematic evaluation of novel research models including new knockout and transgenic mice as well as innovative experimental paradigms. The histology core interacts intimately with other cores. Collaborative efforts with the Functional Testing and Molecular & Digital Imaging Cores provide for a unique ability to assess inner/middle ear function and anatomy in a quick and comparative fashion. This broad spectrum of services provides an appealing environment that encourages collaborative interactions both within the core membership and with investigators from other fields. Anatomy-based research is becoming a lost art with the current emphasis on molecular techniques and many labs can no longer afford the specialized equipment and personnel required to optimally perform these procedures. The Histology Core provides a vital service to ensure that this approach is always available for investigators in our field.